Fix for #829: Under maintenance project should not get back to "Draft…

[niksj]

Fixes 829: Under maintenance project should not get back to "Draft" after maintenance ended

[osarrat]

Hi ! The fix you proposed seems to be partial and not completely correct. I've reported the error of understanding directly in a line of code comment. The fix is also partial because the issue occurs when a user unchecks the "Under maintenance" checkbox and clicks on "Save", then the project model is sometimes shift automatically to "Draft" status. Your fix doesn't seem yet to deal with this case. A bit more work is still required to finish it. :)